1544

2: Edible fruits and nuts

Sandoricum koetjape (Burm.f.) Merr.

Philip. Journ. Sci. Bot. 7: 237 (1912).

MELIACEAE

2n = 22

Melia koetjape Burm.f. (1768), Sandoricum indicum Cav. (1789), Sandoricum nervosum Blume (1825).

Santol, kechapi, sentol (En). Faux mangoustan (Fr). Indonesia: kecapi, ketuat, sentul. Malaysia: sentul, kechapi. Philippines: santol, santor. Burma: thitto. Cambodia: kôm piing riëch. Laos: toongz. Thailand: kra thon (central), sa thon (peninsular), ma tong (northern). Vietnam: sâú.

Santol is a native of Indo-China and western Malesia and is now found naturalized or cultivated throughout tropical Asia, particularly in Indonesia, Malaysia, the Philippines, Thailand and Vietnam. It has also been introduced in other tropical countries.

The fruits are usually eaten fresh, processed into candy, chutney, jam, jelly, marmalade or preserve, or used in flavouring native dishes. Both the rind and the pulp (which may or may not adhere to the seeds) are edible. The fruit varies a lot and either the rind or the pulp may be more substantial and/or palatable. The tree is an excellent shade tree with ornamental value. The wood is utilized for construction, carpentry, and to make household utensils and implements. The fresh leaf when applied to the skin is sudorific and in decoction is used to cure fever. The powdered bark is an effective treatment for ringworm. The roots are employed as an anti-diarrhetic, antispasmodic, carminative, stomachic and are prescribed as a general tonic after childbirth.

No published production data are available. In Thailand, production areas consist of scattered plantings all over the country. In the Philippines, santol is a common backyard tree and small orchards are established in some parts of the country. International trade is minimal; the Philippines export santol in syrup form to the United States and Saudi Arabia.

The tough rind may be thin or thick, and the taste of the pulp ranges from sweet to sour. 'Native' fruit from unselected trees in the Philippines, so-called to contrast with the introduced cultivar 'Bangkok', contains about 53% pulp. It contains per 100 g edible portion: water 83.9 g, protein 0.7 g, fat 1 g, carbohydrates 13.7 g, fibre 1.1 g, ash 0.7 g, calcium 11 mg, phosphorus 20 mg, iron 1.2 mg, potassium 328 mg, and vitamin C 14 mg. The energy value is 247 kJ/100 g.

Semi-deciduous tree, up to 30 m tall and trunk 90 cm in diameter, containing milky latex. Leaves alternate, trifoliolate, long-petiolate; petiole up to 18.5 cm long; leaflets elliptic to oblong-ovate, top leaflet 6—26 cm x 3—16 cm, petiolule 2—9 cm, side leaflets 4—20 cm x 2—15 cm, petiolule up to 1 cm long, pointed at tip, rounded or slightly pointed at base, glossy green above, pale green below. Inflorescences axillary panicles, up to 25 cm long; flowers bisexual, yellowish-green, ca. 1 cm x 1.3 cm; calyx cup-shaped, 5-lobed; petals 5, oblanceolate, 1 cm long; staminal tube cylindrical with 10 split teeth at apex, anthers 10; pistil with a large stigma, a long slender style and a 5-celled ovary, surrounded by a laciniate yellowish disk. Fruit a berry, depressed globose, 5—6 cm diameter, golden yellow, soft hairy; outer fleshy portion thick, tough, flesh-coloured and subacid; inner fleshy portion soft, white, sour to sweet, usually adhering to the seed. Seeds 2—5, obovoid in outline, glossy brown, large; cotyledons red.

Santol seeds germinate about 20 days after sowing. Seedlings grow fast and may start flowering after 5—7 years. Clonally propagated trees may flower 3—4 years after planting. Inflorescences are produced in the axils of young shoots of the main flush, following a brief deciduous or semi-deciduous period in the course of the dry season or a dry spell. If the shoot growth flush is protracted, so is flowering; in the Philippines flowering lasts for about 3 months (January—March). Pollination is by insects; self-incompatibility seems to be the rule as the flowers are protandrous. Relatively few flowers set fruit. Fruit development takes about 5 months and fruit ripens from June—October in the Philippines, May—July in Thailand. Trees may remain productive for 50 years or more.

The former division into 2 species (Sandoricum indicum, yellow santol; Sandoricum nervosum, red santol) was based on a number of characteristics of which only the distinct colour change of the leaves before abscission appears to be consistent: leaves of Sandoricum indicum turn yellow and leaves of Sandoricum nervosum turn red before they are shed. However, there is no clear link with other characteristics used to distinguish the two species, e.g. the contrast between thin rind and substantial sweet pulp, and fruit with thick rind and scanty sour pulp.
A number of cultivars are recognized in Thailand, e.g. 'Barngklarng', 'Eilar', 'Tuptim' and 'Teparod'. The latter may be the cultivar which became popular in the Philippines under the name 'Bangkok', producing fruit with a mean weight of over 250 g against 80 g for fruit from unselected trees. 'Bangkok' is a tetraploid cultivar.

Santol is a hardy plant and thrives without irrigation in areas with a prolonged dry season. The tree grows best in areas with an even distribution of rainfall, but there are no yield data to show whether flowering and fruiting benefit or suffer from this vigour. It is cultivated from sea-level to altitudes exceeding 1000 m. Excellent growth is assured in clay loam and sandy loam soils that are loose and friable with plenty of humus.

Santol can be propagated from seed or through budding, grafting, inarching and marcotting. Seeds are sown 5 cm apart in a seed-bed containing fine sand. When the first pair of leaves has matured, seedlings are transplanted to individual containers. Since germination percentages tend to be high, seeds can also be sown directly into containers. The seedlings may be used as rootstocks in a year or less when they are about 40—50 cm tall. Shield or patch budding and wedge grafting are the commercial methods of propagation.
It is best to plant at the onset of the rainy season. In Thailand tree spacing ranges from 8 m x 5 m to 12 m x 12 m. Close spacing is practised for the intensive orchards in the lowlands of the central delta, where the trees are planted on ridges separated by drainage ditches; the high water table helps to check tree growth. For commercial orchards the latest development is high-density planting with a plant spacing of 4—6 m.

Regular weeding or mulching around the trunk of the tree is recommended. During the first 2—3 years, 2—3 leading branches should be allowed to develop. Regular watering is critical in the year after planting and is also beneficial during the development of flowers and fruits. Fertilization during the first year entails applying 100—200 g ammonium sulphate a month after planting and before the end of the rainy season. Young bearing trees receive 200—500 g complete fertilizer twice a year. Full-grown trees require at least 2 kg complete fertilizer per application to sustain growth and fruit production. In Thailand the young fruit is bagged on the tree to improve the quality and to prevent fruit flies from depositing their eggs.

Pink disease caused by the fungus Corticium salmonicolor is a common disease of santol. The cankers can be thoroughly removed and the wounds dressed with copper fungicides when the trees have shed their leaves, so that the rainy season is entered with a low infection pressure. Nursery plants may be blighted by Phytophthora phaseoli. Soil sterilization or fungicides can control the blight.
The most serious pest of santol is the gall-forming mite Eriophyes sandorici, which can be controlled by spraying with a miticide. Fallen leaves from infested trees should be burned. Oriental fruit flies are also serious pests, especially on cultivars with a thin rind. Bagging of the fruit or baiting the flies are recommended control measures.

The fruits are harvested selectively when they turn golden yellow. They are picked either by climbing the tree or by a net attached to a long bamboo pole.

A 30-year-old seedling tree in the Philippines produces 18 000—24 000 fruits each year. At 80 g per fruit and 100 trees/ha this works out to a theoretical yield of 14—19 t/ha per year.

Immediately after harvest the fruit is sorted and packed in baskets lined with banana leaf-sheaths, ready for transport to the market. The fruit keeps for at least seven days at room temperature.

There is a wide variation among seedling trees in terms of fruit characteristics and tree productivity. The Institute of Plant Breeding at the University of the Philippines at Los Baños evaluates clonal offspring of selected seedling trees. All santol cultivars have resulted from selection among seedling trees. Attempts at crossing the tetraploid santol as female parent with the diploid form as male parent to produce triploid progenies have so far failed because the young fruit aborted.

The sour pulp which is usually discarded when the fruit is eaten fresh has great processing potential, but then the whole fruit should, of course, be processed. For fresh consumption, superior selections/cultivars with sweet pulp have already shown their potential, e.g. in the form of orchards planted with 'Bangkok' in the Philippines. It is not yet clear whether the prospects are best in areas with or without a prominent dry season.

Coronel, R.E., 1986. Promising fruits of the Philippines. 2nd edition. College of Agriculture, University of the Philippines at Los Baños, College, Laguna. pp. 399—415.
Mabberley, D.J., 1985. Florae Malesianae praecursores 67. Meliaceae (Divers Genera). Sandoricum. Blumea 31: 146—152.
Moncur, M.W., 1988. Floral development of tropical and subtropical fruit and nut species. Natural Resources Series No 8, CSIRO, Melbourne. pp. 75—77.
Pimentel, R.B., 1980. Floral biology, fruitset and pollen fertility studies on Sandoricum koetjape (Burm.f.) Merr. Special publications, Department of Horticulture College of Agriculture, University of the Philippines at Los Baños, College, Laguna.
Ramos, A.H., 1972. Santol [Sandoricum koetjape (Burm.f.) Merr., Meliaceae]. In: Cultural directions for Philippine agricultural crops. Vol. 1. Fruits. Public Affairs Office Press, Bureau of Plant Industry, Manila. pp. 209—212.
Sastrapradja, S., Sutisna, U., Panggabean, O., Mogea, J.P., Sukardjo, S. & Sunarto, A.T., 1980. Fruits. Proyek Penelitian Potensi Sumber Daya Ekonomi. LIPI Publication Series No SDE-41. pp. 114—117.
Thamnityakum, T., 1985. The santol plantation of Nonthaburi's gardeners: Thailand. House Agricultural Magazine 9(106): 23—29, 78.

R.C. Sotto

Sotto, R.C., 1991. Sandoricum koetjape (Burm.f.) Merr.. In: Verheij, E.W.M. and Coronel, R.E. (Editors): Plant Resources of South-East Asia No 2: Edible fruits and nuts. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea